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第62頁(yè)

信息發(fā)布者：

C

D

10

218

±3

±2

-6或0

$ \begin{aligned}解：原式&=4m2+12mn+9n2-(4m2-n2) \\ &=4m2+12mn+9n2-4m2+n2 \\ &=10n2+12mn. \\ \end{aligned}$

$ \begin{aligned}解：原式&=[(m+2n)(m-2n)]2 \\ &=(m2-4n2)2 \\ &=m?-8m2n2+16n? \\ \end{aligned}$

$ \begin{aligned}解：原式&=[x-(3y+2)]2 \\ &=x2-2x(3y+2)+(3y+2)2 \\ &=x2+9y2-6xy \\ &=4x+12y+4. \\ \end{aligned}$

$ \begin{aligned}解：原式&=[a-(2b-3c)][a+(2b-3c)] \\ &=a2-(2b-3c)2 \\ &=a2-(4b2-12bc+9c2) \\ &=a2-4b2+12bc-9c2 \\ \end{aligned}$

$ \begin{aligned}解：原式&=x2-16+x2-6x+9 \\ &=2x2-6x-7 \\ \end{aligned}$

$因?yàn)閤=3$

$所以原式=2×32-6×3-7=-7$

$ \begin{aligned}解：原式&=x2-4y2-4x2+4xy-y2+6x2-15xy-2xy+5y2 \\ &=3x2-13xy \\ \end{aligned}$

$將x=-1，y=-2代入$

$得3x2-13xy=3×(-1)2-13×(-1)×(-2)=-23$

C

D

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